Saturday, November 9, 2013

Find sin 2x, cos 2x, and tan 2x from the given information. sec x = 8, x in Quadrant IV.

Cosine is positive in quadrant 4, sine is not.

sec%28x%29=8

Tells is that

r=8 and x=1

so y=sqrt%28r%5E2-x%5E2%29=sqrt%288%5E2-1%5E2%29=3sqrt%287%29

Now we are ready...
sin%282x%29=2sin%28x%29cos%28x%29=2%28-3sqrt%287%29%2F8%29%281%2F8%29=-3sqrt%287%29%2F32
cos%282x%29=2cos%28x%29%5E2-1=2%281%2F8%29%5E2-1=-31%2F32

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